The combination of a contactor and circuit breaker for use in motor control applications is described in U.S. Pat. No. 4,025,883 entitled "Modular Integral Motor Controller" wherein a single pair of separable contacts are employed to interrupt motor current upon occurrence of both long time and short time overcurrent conditions.
U.S. Pat. No. 5,057,962 entitled "Microprocessor-Based Protective Relay System teaches the use of a logic circuit to interrupt motor current upon long time overcurrent conditions by comparing real time motor current to set point data tailored to represent thermal conditions within the motor core and windings.
One example of a logic circuit to control the operation of a circuit breaker upon short time overcurrent conditions and a contactor upon long time overcurrent conditions is found in U.S. Pat. No. 5,448,442 entitled "Motor Controller with Instantaneous Trip Protection".
The state of the art motor controller units employing both circuit breakers and contactors in motor controller operations require custom circuits that are designed for each specific application.
It would be economically advantageous to utilize standard circuit breaker and contactor products without having to customize the circuit breaker, contactor or both to insure proper operation.
One purpose of this invention is to interconnect standard motor controller components by means of a simple and inexpensive electronic module to provide a motor controller that exhibits the benefits of both contactor and circuit breaker protection without significant cost increase.